Geiger counters are interesting and surprisingly useful devices, and you can build one for less than the price of a video game. They can monitor background radiation levels, check household items such as smoke alarms and gas mantles, and provide information about medical treatments. I designed and built my own unit having been diagnosed with cancer in 2017, and it has provided some fascinating insights.
This talk describes the design and construction of a simple Geiger counter with an OLED display and a recording facility, and illustrates some of the science behind medical procedures involving radiation, such as PET scans (Positron Emission Tomography) and radiotherapy.